This invention relates to an on-line inside-quality inspecting device for non-destructively inspecting and measuring the inside-qualities such as sugar forming degree, acidity, etc. of the objects of inspection, such as agricultural products, by projecting beams of light on each of the objects from one side of it and by receiving and spectrally analyzing, on the other side, the light transmitted through the object while these objects of inspection are in process of being conveyed by various transport means.
Known methods for measuring the inside-quality of agricultural products include a reflection light method and a transmission light method. In the reflection light method, information on the inside-quality is detected through a reflection light obtained from the agricultural product by projecting beams of light including near infrared rays on the agricultural product. In the transmission light method, information on the inside-quality is detected from light transmittance through the agricultural product of the light projected on the agricultural product.
As disclosed, for example, in Japanese Laid-Open Patent Application No. HE 6-300681,the reflection light method is arranged to be carried out by projecting beams of light including near infrared rays onto a measuring object and by detecting the information on the inside-quality of the object from light reflected by the object as a result of light projection. The method, therefore, permits use of receiving trays arranged in a conventional screening device as they are.
However, the inside-quality information obtainable by the reflection light method is limited to information on a peripheral part and a part near to it of the agricultural product where the projected light is received. Therefore, this method is not applicable to a fruit having a thick skin, although the method is applicable to a fruit having thin skin, such as peaches and pears. In other words, it has been a problem with this method that, in the event of a fruit having a thick skin, the reflection light obtained gives information only on the quality of a thick skin part but does not give any information on the edible flesh part of the fruit.
The applicant of the present patent application has developed and practicalized an inside-quality inspecting device of the transmission light method which is capable of detecting information on the inside-quality of citrus fruits (oranges), melons, watermelons, etc. having thick skin parts and the honey forming parts, or brown scarred parts existing deep inside of apples or the like. The device developed and practicalized by the applicant is arranged, as disclosed in Japanese Laid-Open Patent Applications No. HE 6-288903 and No. HE 10-202205,to use a transport conveyer having agricultural products receiving trays having receiving seats. Each of the receiving seats is provided with a transmitted light passage which vertically penetrates the central part of the seat. The device is thus arranged to have its light receiving part opposed to the lower side of the center part of the receiving tray, so that the device can be used only for the conveyer of the type using such receiving trays. It has been impossible to use the device in combination with any conveyer that is not using the receiving trays of the above-stated type.
Meanwhile, known inside-quality inspecting devices of the transmission light method include a device disclosed in Japanese Laid-Open Patent Application No. HEI 7-229840.In this device, one light-projecting lamp is arranged as a light source on one side of the transport path of a belt conveyer; a light receiving part is opposed to the light-projecting lamp and arranged on the other side of the transport path at a position where an optical path extends horizontally and rectilinearly across the transport path; light is projected sidewise on each agricultural product under inspection; and light which is transmitted through the agricultural product as a result of light projection is detected by the light receiving part. The device is thus arranged to detect the light sidewise transmitted through the agricultural product. However, since the device uses only one light-projecting lamp, the rays of light projected are limited in intensity and quantity. Therefore, in the case of agricultural products having thick skins, the transmitted light has been too weak for spectral analysis and errors in the results of the spectral analysis have degraded the accuracy of measurement.
Agricultural products are naturally grown products. Generally, the inside-quality, such as sugar content, acidity, degree of ripeness, etc. of each product is not uniform and varies according to its parts on the side of having sunlight or on the shadow side thereof. Measurement values obtained by projecting light from the single projecting lamp, therefore, greatly vary and fluctuate depending on the direction of light projection. It has been thus hardly possible to ensure the measuring accuracy of the inside-quality inspecting device. It has been another shortcoming of the device disclosed in the above-cited Japanese laid-open patent application that a large case is necessary for housing it because the device disclosed is arranged to have a diffraction grating directly connected to its light receiving part.
Further, according to the arrangement disclosed, the optical axis of the light-projecting lamp and the light converging axis of a condenser lens of the light receiving part are on one and the same line. Therefore, intense rays of light come to be straightly incident on the condenser lens to bring about some adverse effect on a spectral light receiving element when the optical axis is not blocked by the agricultural product. To prevent the spectral light receiving element from being affected by the intense rays of light under such a condition, a shutter is provided at a light-projecting port. The shutter is, however, arranged to be left open between front and rear agricultural products under the inside-quality inspection while they are in process of transport and is not to be closed and opened for each of them one by one. When the light is not necessary, such as at the time of a pause, the rays of light of the lamp are arranged to be blocked by means of a shutter solenoid. However, although the light from the light-projecting lamp can be thus blocked, fluctuations of ambient light coming into a dark room through the passage of the agricultural product are allowed to come in as they are through the condenser lens to cause the zero level (of a dark current) of the light receiving element. This has been a shortcoming of the device.
Another shortcoming of the device lies in the following point: In order to have the light penetrate through a thick-skinned agricultural product such as oranges, melons, watermelons and the like, with a single lamp used, the lamp must be arranged to have a high degree of output. However, use of such a high-output lamp necessitates some lamp cooling means as it generates a high temperature. Besides, since the light is converged onto the agricultural product by means of a reflection mirror, the light converging part is heated to have such a high temperature exceeding 500 degrees, which has necessitated use of a heat resisting material and presented the hazard of fire. Further, the filament of the high-output lamp is large. The large filament of the lamp not only makes the light converging arrangement difficult but also has a short service life and cannot be used over a long period of time without lowering the illuminance of the lamp.
If the quantity (intensity) of the projection light is increased to have the transmission light sufficiently obtainable even from inspecting objects which do not readily transmit light, the operational amplifier of a spectral analyzer tends to overflow to make the spectral analysis impossible for inspecting objects which readily transmit the projection light.
Further, the operating state of an on-line inside-quality inspecting device varies with variations in the temperature of the environment taking place at different times of the day, including the morning, noon and evening of the day, and also with the lapse of the operating time. Therefore, in order to stably operate the device over a long period of time, the device must be constantly calibrated. In the case of the above-stated prior art device, however, the light-projecting lamp and the light receiving part are arranged on one and the same optical axis in a state of being opposed to each other. With the device arranged in this manner, it has been impossible to stably carry out such calibration work in cases where the device is set within an imperfect dark room.
It has been a further shortcoming of the device that a calibration curve of the device tends to be caused to deviate by the variations of environment temperature and the lapse of operation time.
This invention is directed to the solution of the problems presented by the prior art device.
It is therefore an object of this invention to provide an inspecting device having a light-projecting part and a light receiving part arranged to be opposed to each other across a transport path of a transport conveyer conveying agricultural products or the like and to permit use of conveyers of varied kinds without limiting the kind of the transport conveyers usable in combination with the inspecting device. In the device, the light-projecting part is arranged to project light onto a wide area of each agricultural product in an increased light quantity across the transport path without much decreasing the illuminance of light over a long period of time, so that the light transmitted to the light receiving part through the product can be efficiently detected irrespective of the degree of light transmissibility of the agricultural object (inspecting object) which varies with the size and kind of the object. It is another object of this invention to provide an inspecting device which includes overflow preventing means for preventing an operational amplifier from overflowing in the event of an inspecting object not allowing the projected light to be readily transmitted therethrough; a light receiving part and calibration means arranged to be not readily affected by disturbance light; and correction means for correcting the deviations of a calibration curve caused by deterioration due to aging, etc., so that inside-quality of the object can be inspected and measured in a highly accurate and reliable manner.
To attain the above-stated objects, this invention is characterized as described below:
In an inside-quality inspecting device according to this invention, light-projecting means is set on one side of the transport path of a transport conveyer which conveys objects of inspection one by one while light receiving means is set on the other side of the transport path and opposed to the light-projecting means across the transport path. Light is projected on each inspecting object from one side thereof while the object is in process of transport. The inside-quality of the object is then inspected by receiving the light transmitted through the inside of the object and coming out from the other side thereof and by performing spectral analysis on the light transmitted. The device according to this invention is characterized in that the light-projecting means is arranged to use a plurality of light-projecting lamps and to concentratedly project beams of light obliquely on each inspecting object, from different positions and at different angles covering a wide range of the surface areas on one side of the object from an obliquely front are to an obliquely rear area when the object is at an inspecting position on the transport path; and the light receiving means is provided with a light passage opening-and-closing mechanism in which a shutter is arranged to open and close the passage of light between a light receiving window of a condenser lens and a light inputting face of an optical fiber which is arranged to lead light to a spectroscope.
According to this invention, the beams of light are concentratedly and almost. uniformly projected over the whole surface of the inspecting object on one side thereof by using many lamps while the object is in the position to be inspected. Therefore, a large quantity of light can be projected from the many lamps to cover a large area on both the sunny side of the object where the object has sufficiently basked in the sunlight and the shadow side of it where it has not sufficiently had the sunlight even in the case where the sugar content is unevenly distributed to the sunny and shadow sides. As a result, the light transmitted through the various internal parts of the inspecting object carries averaged information on the internal quality of it when the transmitted light exits on the exit side of the object. The transmitted light is received and subjected to spectral analysis made by the light receiving means, so that the internal quality of the inspecting object can be adequately inspected.
The shutter disposed between the light receiving window of the transmitted-light-receiving condenser lens and the light inputting face of the optical fiber is arranged to be left closed when the inspecting object on the move comes to the fore end and the rear end of an inspection part of the transport path in the direction of travel. With the shutter arranged in this manner, the light transmitted can be unpitied to the light receiving means only from the central part of the object. In case where there is no inspecting object, the shutter remains closed to allow no light to enter into the spectral analyzer, so that the analyzer can be prevented from being affected by an increase in temperature.
An inside-quality inspecting device arranged according to this invention is characterized in that the condenser lens of the light receiving means is provided with a lens hood for securing a visual field in front of the condenser lens on the objective side thereof; a light receiving window which has a dust-proof structure with a transparent glass part arranged in front of the lens hood; and means for moving a white level calibration plate back and forth in front of the light receiving window for calibration.
According to the inventive arrangement, the condenser lens is provided with the lens hood which opens toward the center of the inspecting object to prevent an adverse effect of disturbance light and the light receiving window which restricts a visual field to a size which has only the transmitted light coming from the front of the condenser lens. The white level calibrating plate which comes to or retreats from the front of the light receiving window is arranged to permit calibration work on the overall output value of the device, before the start of operation, at a pause of the operation or after a pause of operation, to avoid such errors that might be caused by variations of environment temperature and deteriorations of lamps and the optical system of the device.
An inside-quality inspecting device arranged according to this invention is characterized in that the device is provided with an orifice plate. The orifice plate is arranged within the above-stated lens hood of the condenser lens to restrict and define a light passage area in such a way as to have the light receiving optical axis of the optical system at the center of the light passage area, so that scattering light and flares can be prevented from taking place.
The above-stated inspecting device according to this invention effectively removes all lights other than the light transmitted through the inspecting object, such as disturbance light and flares caused by scattering light entering into the lens hood from the light receiving window of the condenser lens and by irregular surface reflection taking place inside of the lens hood. The arrangement thus enhances the accuracy and reliability of the results of the spectral analysis.
An inside-quality inspecting device according to this invention is characterized in that the inventive device is provided with air cooling means. The air cooling means has a cooling air blowing duct and an air nozzle which blows cooling air toward the lens hood of the condenser lens and the white level calibrating plate in its stand-by position. The air cooling means is thus arranged to discharge heat caused by the rays of light coming from the light-projecting lamps to the condenser lens and the white level calibrating plate by blowing air from an air blower into the air blowing duct.
According to the above-stated arrangement, a gradual increase of temperature due to the beams of light from the light-projecting lamps can be suppressed to prevent the optical characteristics of the device from varying due to changes of temperature, so that the stability of results of spectral analysis can be maintained.
An inspecting device according to this invention is characterized in that, in the inventive device, each of the plurality of light-projecting lamps is provided with a reflecting mirror having a parabolic surface arranged to form a beam angle at which a focal point is obtained where the inspecting object is at its inspecting position. The front side of each of the lamps is sealed with a heat resisting glass part. These sealed lamps are arranged to have their light-projecting axes deviate from each other at such angles and positions that beams of light passing through the focal point do not rectilinearly come into the light receiving optical axis of the condenser lens of the light receiving means.
According to this invention, the plurality of light-projecting lamps are arranged to concentratedly project beams of light with their focal points located at the object position. This arrangement permits efficient use of relatively small lamps. Each light-projecting lamp has a sealed front, which acts to keep the reflecting power of the reflecting mirror not decreasing. The optical axes of the light-projecting lamps are arranged to deviate from each other at such angles that cause their beams of light not to rectilinearly enter into the light receiving optical axis of the condenser lens. By virtue of that arrangement, the device is not affected by any light that straightly passes through the inside of the inspecting object without diffusing inside of the object.
An inspecting device according to this invention as further defined in accordance with the invention is characterized in that each of the plurality of light-projecting lamps is provided with air cooling means. The air cooling means includes a cooling air blowing duct and an air nozzle which are arranged to send air to a sealed part inserted into a socket at each of the light-projecting lamps to prevent overheat by dissipating heat generated by the lamp body.
With the cooling means arranged in this manner according to this invention, each of the lamps which is in a state of having its front side sealed is air cooled by applying air from the nozzle to the sealed part. The arrangement thus effectively prevents overheat to make the service lives of the light-projecting lamps longer.
An inspecting device according to this invention is also characterized in that the plurality of light-projecting lamps are provided with projecting light quantity adjusting means for increasing or decreasing the number of lamps to be lighted up in such a way as to increase or decrease the quantity of light to be projected according to the size, item, kind and rate of light transmission of the inspecting object.
With the device arranged to include the projecting light quantity adjusting means, as mentioned above, the number of light-projecting lamps to be lighted up for inspection can be changed according to the item, kind and difference in rate of light transmission (size) of the inspecting object. The arrangement makes the device applicable to many items of inspecting objects including, for example, watermelons and melons which have thick skins and do not readily allow the inspection light to be transmitted through the inside of them; oranges which have a medium thickness of skin; tomatoes and pears which have thin skins to readily transmit light; apples; peaches; and so forth.
An inspecting device according to this invention is further characterized in that the device is provided with lifting-and-lowering means, by which a lamp box containing therein the plurality of light-projecting lamps of the light-projecting means is caused to be vertically moved upward or downward by remote control, so that the light-projecting height of the lamps can be adjusted by remote control according to the size of the inspecting object which varies with the item and kind thereof
With the inside-quality inspecting device arranged to include the lifting-and-lowering means, the inspecting object can be easily and promptly switched from one over to another among different items and kinds of inspecting objects having different sizes. This arrangement is a great advantage in cases where the device must be used f or many different items as it facilitates stepwise change-over from one object to another.
An inspecting device according to this invention is still further characterized in that the light receiving means of the device defined is provided with filter change-over inserting means. The filter change-over inserting means is arranged to be operated to reduce the quantity of light incident on the optical fiber by selectively inserting any of light reducing filters of different kinds into the passage of light between the light receiving window of the condenser lens and the light inputting face of the optical fiber.
With the inside-quality inspecting device arranged in the above-stated manner according to this invention, even where the amplification degree of the operational amplifier of the spectral analyzer has been adjusted for such an inspecting object that allows only a small quantity of transmitted light to enter the light receiving means, the operational amplifier can be prevented from overflowing to hinder the spectral analysis by reducing and limiting the incoming light by means of the light reducing filter when the object giving a small quantity of transmitted light is changed over to an object which gives a large quantity of transmitted light.
An inspecting device according to this invention is also characterized in that the device having the light-reducing-filter change-over inserting means is provided with remote control change-over means for selectively operating by remote control a light-reducing-filter mounting plate on which a plurality of light reducing filters of different light reducing rates are mounted.
With the device arranged in this manner according to this invention, the stepwise change-over action on the light reducing filters can be easily carried out in a very short period of time when the object of inspection is changed from one kind over to another.
An inspecting device according to this invention is further characterized in that the shutter disposed between the light converging window of the condenser lens and the light inputting face of the optical fiber is arranged within a dark box which contains the passage of light and has its surrounding part tightly sealed. The shutter is thus arranged to be opened and closed for each of the inspecting objects one by one every time the object comes to pass the inspecting device. In other words, the shutter is operated to be opened when the inspecting object is in the inspecting position and to be closed to allow no light to come into the spectroscope when the inspection is not required.
With the invented device arranged in this manner, the spectroscope (spectral analyzer) is kept shielded from light except when the transmitted light is allowed to enter the center part of the inspecting object in the inspecting position. Since no light is allowed to come into the spectroscope to prevent it from being affected by a rise of temperature or the like, the zero level of the light receiving element of the device stably remains constant. The light receiving element always rises from its zero level to give a reliable inspection output every time an inspecting object is inspected.
An inspecting device according to this invention is still further characterized in that the shutter disposed between the light converging window of the condenser lens and the light inputting face of the optical fiber is arranged within a dark box which contains the passage of light and is shielded from its surroundings. The shutter is provided with shutter driving means which is arranged to have the shutter normally open and closed only when a dark level detecting action is performed before or after the white level calibrating plate is operated. The control circuit of a detecting light receiving element disposed on the rear side of the spectroscope is provided with an electronic shutter circuit, which is arranged to cause an electronic shutter to act every time one inspecting object passes the inspecting device.
The electronic shutter circuit which is included in the control circuit of the light receiving element on the rear side of the spectroscope is arranged to electrically perform time control over detection of light transmitted through each of inspecting objects in such a way as to discharge and clear the electric charge of detection. The electronic shutter thus operates without being affected by any residual detection electric charge obtained immediately before the detection. Since the electronic shutter circuit requires no mechanical moving part, the inspecting device can be continuously operated at a high speed so that the processing capability of the device per unit time can be enhanced by increasing the speed of the transport conveyer.
An inspecting device according to this invention is also characterized in that the device is provided with a mechanism for moving a quality reference material forward and backward in place of the white level calibrating plate, before or after the latter is moved forward and backward, in front of the light receiving window of the condenser lens of the light receiving means having the lens hood. The quality-reference-material moving mechanism is used as means for correcting aging fluctuations of the calibration curve of the spectral analyzer on the basis of variations taking place in light transmitted through the quality reference material.
In the inspecting device arranged according to this invention as mentioned above, light transmitted through a vessel which contains therein the quality reference material is detected in association with the calibration work performed with the white level calibrating plate. Then, aging fluctuations and variations of the calibration curve due to continuous lighting, continuous operation or the like of the inside-quality inspecting device and changes in the ambient temperature and environmental conditions of the device can be adequately corrected on the basis of the transmitted light thus obtained through the quality-reference-material containing vessel.
An inspecting device according to this invention is also characterized in that the mechanism for moving the quality reference material forward and backward is arranged to selectively move a plurality of quality reference materials by inching them one by one.
In carrying out component analysis for a plurality of components in respect to the sugar forming degree, the acidity, etc. of the inspecting object, the above-stated arrangement according to this invention permits correction of aging variations of the calibrating curve in accordance with the actual situation.
An inspecting device according to this invention is also characterized in that the quality reference material is a solid material.
According to this invention, a solid material having an absorbing characteristic in a wavelength band close to that of the inspecting object is employed as the quality reference material. The use of such a material permits calibration work stably performed as it little deteriorates even when it is used over a long period of time.
An inspecting device according to this invention is characterized in that the quality reference material is a liquid material contained in a vessel.
According to this invention, a liquid material having a quality component equal to that of the inspecting object is employed as the quality reference material. Such a liquid material can be easily obtained, so that the calibration work can be carried out in accordance with the actual situation.
An inspecting device according to this invention is further characterized in that the device is provided with lifting-and-lowering means for vertically moving the mount base of the light receiving means by remote control. The lifting-and-lowering means is arranged to permit adjustment of the height of a light receiving optical axis by remote control according to the size of the inspecting object which varies with the item and kind of the inspecting object.
By virtue of the arrangement according to this invention, the inspecting object can be easily and promptly switched from one over to another among different items and kinds of inspecting objects having different sizes.